The present invention relates to resin laminates, and in particular, to a laminate composed of a fiberglass-embedded solid resin lamina bonded to a resin block.
Fiberglass-embedded resin laminates are widely used today in molded structure applications, such as in forming boat hulls and vehicle bodies. The laminates generally comprise one or more fiberglass-embedded resin laminae bonded to a block, or core.
In forming a laminate of the type just described, it is usual to prepare a layer of uncured resin embedded with fiberglass, and to place the block against the uncured liquid layer. After rolling the outer surface of the layer to remove any pockets of air trapped between the block and layer, the resin forming the layer is permitted to harden, or cure, to produce a solid resin lamina secured to the block.
A material which has been successfully used as a core in such laminates includes pieces of balsa wood held together with a netting. However, the use of balsa wood has been restricted because it is generally in short supply and consequently quite expensive.
More recently, homogeneous polyurethane foam in slab form has been used as a block material in resin laminates of the above-described types. Although relatively inexpensive, the polyurethane block has not been entirely satisfactory in that polyurethane material having a suitable stiffness for use in this application, is composed primarily of closed cells. Consequently, this material is relatively impermeable to the layer of uncured polyester resin forming the resin lamina. This may prevent a satisfactory bond being formed between the resin lamina and the block.
The low permeability of the polyurethane core may also prevent satisfactory removal of any air trapped between the uncured resin and the core. Such air creates interfacial regions at which the lamina and core are unbonded.
The present invention concerns a method for forming resin laminates which largely overcomes the above-described disadvantages and problems.
By this method, a core, or block is prepared comprising a matrix composed of a solid resin matrix material and particles composed of a solid resin filler material distributed in the matrix. A layer of a solution of a relatively unpolymerized resin which forms the resin lamina is placed against a surface of the block. Such liquid resin is effective to dissolve the filler particles adjacent such block surface, forming recesses, or voids in the block matrix. These recesses become at least partially filled with the unpolymerized resin solution. At the same time any air trapped between the layer and the block tends to be sequestered in such recesses. The resin is then cured to form a solid resin lamina which is joined with polymerized resin contained in the voids in the block matrix to secure the lamina to the core.
In a preferred embodiment, a block composed of a polyurethane foam matrix having filler particles of expanded polystyrene distributed therein is prepared. A layer of a solution of polyester in styrene solvent, with fiberglass embedded therein, is formed and placed against a surface of the block. The styrene solvent is effective to solubilize the polystyrene particles adjacent such block surface, leaving recesses distributed within the polyurethane matrix. These recesses become at least partially filled with the polyester solution. Upon curing, the polyester solution forms a solid polyester lamina joined with solid polyester resin filling the block recesses.
It is an object of the present invention to provide a novel method for forming a resin laminate which largely overcomes problems and limitations associated with prior art methods of forming resin laminates.
It is yet another object of the invention to provide method for forming a resin laminate in which a layer of uncured liquid resin is placed against a surface of the block, such application producing recesses in the surface of the block, which recesses become at least partially filled with the uncured liquid resin prior to curing.
It is yet another object of the invention to provide a method of forming a resin laminate which is substantially free of trapped air at the lamina/block interface.
These and other objects and features of the present invention will now be more fully described with reference to the following detailed description of a preferred embodiment of the invention, and the accompanying drawings.